[Users] Hosted-Engine purpose for gateway check?

[Andrew Lau]

On Sun, Apr 6, 2014 at 4:55 PM, Yedidyah Bar David <didi at redhat.com> wrote:
> ----- Original Message -----
>> From: "Andrew Lau" <andrew at andrewklau.com>
>> To: "users" <users at ovirt.org>
>> Sent: Sunday, April 6, 2014 3:10:19 AM
>> Subject: [Users] Hosted-Engine purpose for gateway check?
>>
>> Hi,
>>
>> I was recently playing around with the new ovirt 3.4 ga, I'm very
>> happy all those issues I reported got fixed :D
>>
>> I found a new issue regarding the use of PREFIX vs NETMASK which I've
>> uploaded here https://bugzilla.redhat.com/show_bug.cgi?id=1084685
>>
>> Anyway -- I'm wondering what is the purpose for the gateway check in
>> the hosted-engine setup? In my test case, I had the following NIC
>> configuration
>>
>> eth0 - public (has gateway)
>> eth1 - management
>> eth1.1 - storage
>> eth2 - vm data (no IP address)
>>
>> So during the hosted engine install, it will not let me assign eth2 as
>> the NIC because it has no IP address or gateway. So I proceed to use
>> eth1 instead as, as it has an IP address but again that would fail
>> because no gateway. Luckily I have a L3 switch, so I put up a gateway
>> for eth1 and that solved that issue.
>>
>> What is the gateway check supposed to achieve? I also tried to put in
>> my eth0's IP address as the gateway but it still failed because of
>> those config issues. If management/ovirtmgmt/vmdata are all on a L2
>> switch environment, effectively there becomes no gateway and it
>> prevents the installation.
>
> It actually does not need to really be a gateway. It's used only as
> part of a calculation trying to assess the liveliness of the host.
> See [1] for details, especially pages 33-34.
>
> [1] http://www.ovirt.org/images/8/88/Hosted_Engine_Deep_Dive.pdf
> --
> Didi

I've recall reading that pdf before - however my comments are a little
aimed towards why does the setup require the GATEWAY=x be in the
ifcfg-ethx file when it also asks for the gateway in the otopi setup.
It seems a little redundant and also prevents the ability to proceed
with the setup if you're in a L2 switch environment.

The hosted-engine VM will require a gateway as it only has one nic and
needs to be publicly accessible, so let's say we have:
eth1 -> ovirtmgmt (172.16.0.10) -> hosted-engine (192.168.100.10 w/
192.168.100.1 as gateway)

Isn't 192.168.100.1 the gateway we want to be checking for?

Although now that I think of it, I'm confused where the gateway check
has it's example scenario, is it just for checking to make sure the
hosted-engine will be externally accessible? Wouldn't it also work to
do something like ethtool and check the link exists instead.